Beneficial Functions of Middleboxes
draft-dolson-plus-middlebox-benefits-03

Request for posting confirmation emailed to previous authors: David Dolson , Juho Snellman , Mohamed Boucadair , Christian Jacquenet RFC 6747                      ILNPv4 ARP                  November 2012

  is based upon, and backwards compatible with, IPv6.  The term ILNPv4
  refers precisely to an instance of ILNP that is based upon, and
  backwards compatible with, IPv4.

  Many engineering aspects common to both ILNPv4 and ILNPv6 are
  described in [RFC6741].  A full engineering specification for
  either ILNPv6 or ILNPv4 is beyond the scope of this document.

  Readers are referred to other related ILNP documents for details
  not described here:

      a) [RFC6740] is the main architectural description of ILNP,
        including the concept of operations.

      b) [RFC6741] describes engineering and implementation
        considerations that are common to both ILNPv4 and ILNPv6.

      c) [RFC6742] defines additional DNS resource records that
        support ILNP.

      d) [RFC6743] defines a new ICMPv6 Locator Update message
        used by an ILNP node to inform its correspondent nodes
        of any changes to its set of valid Locators.

      e) [RFC6744] defines a new IPv6 Nonce Destination Option
        used by ILNPv6 nodes (1) to indicate to ILNP correspondent
        nodes (by inclusion within the initial packets of an ILNP
        session) that the node is operating in the ILNP mode and
        (2) to prevent off-path attacks against ILNP ICMP messages.
        This Nonce is used, for example, with all ILNP ICMPv6
        Locator Update messages that are exchanged among ILNP
        correspondent nodes.

      f) [RFC6745] defines a new ICMPv4 Locator Update message
        used by an ILNP node to inform its correspondent nodes
        of any changes to its set of valid Locators.

      g) [RFC6746] defines a new IPv4 Nonce Option used by ILNPv4
        nodes to carry a security nonce to prevent off-path attacks
        against ILNP ICMP messages and also defines a new IPv4
        Identifier Option used by ILNPv4 nodes.

      h) [RFC6748] describes optional engineering and deployment
        functions for ILNP.  These are not required for the operation
        or use of ILNP and are provided as additional options.

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1.2.  Terminology

  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
  NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
  "OPTIONAL" in this document are to be interpreted as described
  in [RFC2119].

2.  ARP Extensions for ILNPv4

  ILNP for IPv4 (ILNPv4) is merely a different instantiation of the
  ILNP architecture, so it retains the crisp distinction between the
  Locator and the Identifier.  As with ILNPv6, only the Locator
  values are used for routing and forwarding ILNPv4 packets
  [RFC6740].  As with ILNP for IPv6 (ILNPv6), when ILNPv4 is used
  for a network-layer session, the upper-layer protocols (e.g.,
  TCP/UDP pseudo-header checksum, IPsec Security Association) bind
  only to the Identifiers, never to the Locators [RFC6741].

  However, just as the packet format for IPv4 is different to IPv6,
  so the engineering details for ILNPv4 are different also.  While
  ILNPv6 is carefully engineered to be fully backwards-compatible
  with IPv6 Neighbor Discovery, ILNPv4 relies upon an extended
  version of the Address Resolution Protocol (ARP) [RFC826], which
  is defined here.  While ILNPv4 could have been engineered to avoid
  changes in ARP, that would have required that the ILNPv4 Locator
  (i.e., L32) have slightly different semantics, which was
  architecturally undesirable.

  The packet formats used are direct extensions of the existing
  widely deployed ARP Request (OP code 1) and ARP Reply (OP code 2)
  packet formats.  This design was chosen for practical engineering
  reasons (i.e., to maximise code reuse), rather than for maximum
  protocol design purity.

  We anticipate that ILNPv6 is much more likely to be widely
  implemented and deployed than ILNPv4.  However, having a clear
  definition of ILNPv4 helps demonstrate the difference between
  architecture and engineering, and also demonstrates that the
  common ILNP architecture can be instantiated in different ways
  with different existing network-layer protocols.

2.1.  ILNPv4 ARP Request Packet Format

  The ILNPv4 ARP Request is an extended version of the widely
  deployed ARP Request (OP code 1).  For experimentation purposes,
  the ILNPv4 ARP Request OP code uses decimal value 24.  It is
  important to note that decimal value 24 is a pre-defined,
  shared-use experimental OP code for ARP [RFC5494], and is not

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  uniquely assigned to ILNPv4 ARP Requests.  The ILNPv4 ARP Request
  extension permits the Node Identifier (NID) values to be carried
  in the ARP message, in addition to the node's 32-bit Locator
  (L32) values [RFC6742].

        0        7        15      23      31
        +--------+--------+--------+--------+
        |      HT        |        PT      |
        +--------+--------+--------+--------+
        |  HAL  |  PAL  |        OP      |
        +--------+--------+--------+--------+
        |        S_HA (bytes 0-3)          |
        +--------+--------+--------+--------+
        | S_HA (bytes 4-5)|S_L32 (bytes 0-1)|
        +--------+--------+--------+--------+
        |S_L32 (bytes 2-3)|S_NID (bytes 0-1)|
        +--------+--------+--------+--------+
        |        S_NID (bytes 2-5)        |
        +--------+--------+--------+--------+
        |S_NID (bytes 6-7)| T_HA (bytes 0-1)|
        +--------+--------+--------+--------+
        |        T_HA (bytes 3-5)          |
        +--------+--------+--------+--------+
        |        T_L32 (bytes 0-3)        |
        +--------+--------+--------+--------+
        |        T_NID (bytes 0-3)        |
        +--------+--------+--------+--------+
        |        T_NID (bytes 4-7)        |
        +--------+--------+--------+--------+

    Figure 2.1: ILNPv4 ARP Request packet format

  In Figure 2.1, the fields are as follows:

    HT      Hardware Type (*)
    PT      Protocol Type (*)
    HAL    Hardware Address Length (*)
    PAL    Protocol Address Length (uses new value 12)
    OP      Operation Code (uses experimental value OP_EXP1=24)
    S_HA    Sender Hardware Address (*)
    S_L32  Sender L32  (* same as Sender IPv4 address for ARP)
    S_NID  Sender Node Identifier (8 bytes)
    T_HA    Target Hardware Address (*)
    T_L32  Target L32  (* same as Target IPv4 address for ARP)
    T_NID  Target Node Identifier (8 bytes)

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  The changed OP code indicates that this is ILNPv4 and not IPv4.  The
  semantics and usage of the ILNPv4 ARP Request are identical to the
  existing ARP Request (OP code 2), except that the ILNPv4 ARP Request
  is sent only by nodes that support ILNPv4.

  The field descriptions marked with "*" should have the same values as
  for ARP as used for IPv4.

2.2.  ILNPv4 ARP Reply Packet Format

  The ILNPv4 ARP Reply is an extended version of the widely deployed
  ARP Reply (OP code 2).  For experimentation purposes, the ILNPv4 ARP
  Request OP code uses decimal value 25.  It is important to note that
  decimal value 25 is a pre-defined, shared-use experimental OP code
  for ARP [RFC5494], and is not uniquely assigned to ILNPv4 ARP
  Requests.  The ILNPv4 ARP Reply extension permits the Node Identifier
  (NID) values to be carried in the ARP message, in addition to the
  node's 32-bit Locator (L32) values [RFC6742].

        0        7        15      23      31
        +--------+--------+--------+--------+
        |      HT        |        PT      |
        +--------+--------+--------+--------+
        |  HAL  |  PAL  |        OP      |
        +--------+--------+--------+--------+
        |        S_HA (bytes 0-3)          |
        +--------+--------+--------+--------+
        | S_HA (bytes 4-5)|S_L32 (bytes 0-1)|
        +--------+--------+--------+--------+
        |S_L32 (bytes 2-3)|S_NID (bytes 0-1)|
        +--------+--------+--------+--------+
        |        S_NID (bytes 2-5)        |
        +--------+--------+--------+--------+
        |S_NID (bytes 6-7)| T_HA (bytes 0-1)|
        +--------+--------+--------+--------+
        |        T_HA (bytes 3-5)          |
        +--------+--------+--------+--------+
        |        T_L32 (bytes 0-3)        |
        +--------+--------+--------+--------+
        |        T_NID (bytes 0-3)        |
        +--------+--------+--------+--------+
        |        T_NID (bytes 4-7)        |
        +--------+--------+--------+--------+

    Figure 2.2: ILNPv4 ARP Reply packet format

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  In Figure 2.2, the fields are as follows:

    HT      Hardware Type (*)
    PT      Protocol Type (*)
    HAL    Hardware Address Length (*)
    PAL    Protocol Address Length (uses new value 12)
    OP      Operation Code (uses experimental value OP_EXP2=25)
    S_HA    Sender Hardware Address (*)
    S_L32  Sender L32  (* same as Sender IPv4 address for ARP)
    S_NID  Sender Node Identifier (8 bytes)
    T_HA    Target Hardware Address (*)
    T_L32  Target L32  (* same as Target IPv4 address for ARP)
    T_NID  Target Node Identifier (8 bytes)

  The changed OP code indicates that this is ILNPv4 and not IPv4.  The
  semantics and usage of the ILNPv4 ARP Reply are identical to the
  existing ARP Reply (OP code 2), except that the ILNPv4 ARP Reply is
  sent only by nodes that support ILNPv4.

  The field descriptions marked with "*" should have the same values as
  for ARP as used for IPv4.

2.3.  Operation and Implementation of ARP for ILNPv4

  The operation of ARP for ILNPv4 is almost identical to that for IPv4.
  Essentially, the key differences are:

      a) where an IPv4 ARP Request would use IPv4 addresses, an ILNPv4
        ARP Request MUST use:
        1. a 32-bit L32 value (_L32 suffixes in Figures 2.1 and 2.2)
        2. a 64-bit NID value (_NID suffixes in Figures 2.1 and 2.2)

      b) where an IPv4 ARP Reply would use IPv4 addresses, an ILNPv4 ARP
        Reply MUST use:
        1. a 32-bit L32 value (_L32 suffixes in Figures 2.1 and 2.2)
        2. a 64-bit NID value (_NID suffixes in Figures 2.1 and 2.2)

  As the OP codes 24 and 25 are distinct from ARP for IPv4, but the
  packet formats in Figures 2.1 and 2.2 are, effectively, extended
  versions of the corresponding ARP packets.  It should be possible to
  implement this extension of ARP by extending existing ARP
  implementations rather than having to write an entirely new
  implementation for ILNPv4.  It should be emphasised, however, that OP
  codes 24 and 25 are for experimental use as defined in [RFC5494], and
  so it is possible that other experimental protocols could be using
  these OP codes concurrently.

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3.  Security Considerations

  Security considerations for the overall ILNP architecture are
  described in [RFC6740].  Additional common security considerations
  applicable to ILNP are described in [RFC6741].  This section
  describes security considerations specific to the specific ILNPv4
  topics discussed in this document.

  The existing widely deployed Address Resolution Protocol (ARP) for
  IPv4 is a link-layer protocol, so it is not vulnerable to off-link
  attackers.  In this way, it is a bit different than IPv6 Neighbor
  Discovery (ND); IPv6 ND is a subset of the Internet Control Message
  Protocol (ICMP), which runs over IPv6.

  However, ARP does not include any form of authentication, so current
  ARP deployments are vulnerable to a range of attacks from on-link
  nodes.  For example, it is possible for one node on a link to forge
  an ARP packet claiming to be from another node, thereby "stealing"
  the other node&